Functionalized materials, such as functionalized hydrogel polymers or particles, may be employed in a variety of applications to modify the properties of a surface or substrate of interest. For example, a surface may be modified to prevent a particular material from binding or adhering to a surface, or can be modified to a change in response to external stimuli.
Silica hydrogel particles functionalized with polyethylene glycol have been provided as materials to modify surfaces or substrates. Hydrogel silica is currently prepared by: (1) silanation reactions, e.g., isocyanate or ether reactions of alkoyxilanes to PEG urethanes; and (2) grafting to silica PEG moieties prepared by an amino coating (e.g., bis-trimethoxysilylpropylamine) followed by amide formation using N-succimidyl ester of methoxy PEG carboxylic acid. Functionalized silica formed by previous methods, however, do not exhibit good stability in either aqueous or organic media, including in the presence of salts such as 5% sodium chloride in ortho-chlorophenol. Additionally, the efficiency of these processes is low, particles tend to aggregate, or the particles are sticky in a dry state or agglomerate in slurry formulations.